This invention relates to methods and apparatus for recovering livestock feed supplements from animal wastes. More particularly, the present invention relates to methods and apparatus for separating the solids and liquids from animal wastes from a flush-type facility and the treatment of these separated materials in a manner suitable for recycling as animal feed supplements. The present invention is particularly useful for confinement feeding facilities such as for feeding of livestock.
As evidenced in recent years the world demand for feedstuffs, usually considered to be livestock feed ingredients, has outstripped supply at least at historic price levels. As the world population continues to increase, and the living standards of these populations also increases, upward price exertions will remain on those feed ingredients for which livestock and people directly compete. All phases of the cattle producing industry have been continually cost-price sensitive. The cost of energy, roughage and protein sources available to the cattle industry have significantly increased and the value of the finished product has been drastically reduced. It is imperative that production costs be reduced by lower ingredient costs or improving efficiencies.
The concentration of production and availability of feed grain and cellulose in certain geographical areas such as the so-called Corn Belt of the United States indicates an economic advantage in raising and feeding livestock in those areas. For various reasons such as protection from climatic hazards, it is particularly attractive to feed such livestock in confinement. Wherever there is proximity to more densely populated areas, the control of air and water pollution relative to such confinement feeding systems is further important particularly relative to the waste handling and treatment. Thus, it is attractive to provide systems which permit recycling of the wastes as animal feed supplements.
Certain classes of livestock are much more inefficient users of feedstuffs than others. For instance, beef cattle on a fattening ration require at least seven pounds of ration (10% moisture) to produce one pound of gain. According to the National Academy of Science investigations on nutrient requirements of beef cattle, beef cattle require an equal amount of energy for production and body maintenance if they are performing at a near optimal level. Therefore, only 28 1/2% of all of the feed consumed by beef cattle on a fattening ration is actually utilized. The remainder is passed through in the form of animal excrement.
Livestock waste continues to represent a major problem to society and to the livestock feeding industry. To comply with pollution regulations, many livestock operators have improved their facilities to meet these requirements, but their production costs have also increased. The most practical solution to the problems of pollution and increased ration costs is to reclaim, process and recycle the waste from cattle that are being fed in confinement feed lot facilities. Accordingly, various efforts have been directed towards waste recycling in the agricultural industry. For many years cattle feeders have allowed swine to follow cattle in the feed lot. The purpose of this practice was to allow swine to recover a portion of the undigested solids from the cattle waste and convert them into pork. Considerable research, and practical application, has been conducted in the area of recycling poultry waste litter through other classes of livestock. Further, one system for producing feed supplements from poultry is shown in U.S. Pat. No. 3,813,288 by Stribling et al.
During recent years many research projects have been conducted to measure the performance of beef cattle that were fed a ration that contains processed beef cattle waste as a portion of their ration. The premise behind these research tests was to substitute not only energy, but all or a portion of the protein in the ration with protein derived from beef cattle waste. It would appear that feedlot cattle waste when properly collected and processed can be included to make up a part of cattle rations and the performance of cattle on feed is not adversely affected.
Numerous chemical tests have been conducted on feedlot cattle waste to determine levels of protein, dry matter digestibility, calcium, etc. Such research has determined that the amount of protein in fresh feedlot cattle excrement was 6.01%. When converted to a dry matter basis this excrement contained 30.74% protein.
Assuming that an 850 pound steer consumes 21.50 pounds of air dry ration (10% moisture) per day, along with a 28 1/2% utilization factor, only 5.50 pounds of a typical "hot feedlot ration" is utilized by the animal. The remainder of the ration, 13.85 pounds, is passed through in the excrement. As shown in certain "in-vitro" tests, about 70% of the dry matter in this portion of the ration passed through the animal undigested. On a dry matter analysis the digestibility of cattle excrement compares favorably to typical corn silage.
Recent research conducted at Iowa State University has shown that cattle performance when fed ensiled waste excrement is equal to the preformance of cattle that were fed whole-plant corn silage. Thus, there is a tremendous economic potential to the confinement cattle feeding industry if the undigested solid portion of the ration is reclaimed.
Summarizing, various efforts have been applied to recover the food value from the animal wastes as supplements. For confinement cattle feeding barns, there are further a variety of flushable flume configurations for recovering wastes such as are shown in U.S. Pat Nos. 2,233,766 by Bogert, 3,137,270 by Rigertink et al and 3,530,831 by Conover. Further, oxidation of these wastes such as through intensive aeration in storage reservoirs has been pursued. Various methods of inducing air into such collected wastes have also been used. Some research has indicated that up to 50% of the animal wastes from feed lot cattle can be recycled as food supplements except for the final month or two before marketing. Various processes of treatment and silage storage have been suggested, and the recovered silage ration indicates weight gains comparable to cattle fed on whole corn silage ration supplemented with various other additives. Some examples of treatment and separation systems can be found in U.S. Pat. Nos. 2,270,869 by Ditto et al, 3,462,275 by Bellamy and 3,633,547 by Stevens et al. The Stevens et al patent shows a closed loop type confinement feeding system wherein fermented and sterilized solids are automatically added to the feed slurry.